The present invention relates to a graduation reproduction in an optical recording for image processing applicable to information-related field, printing-related field and others.
The tone reproducibility is an important factor in making a high-quality image, and hence, various devices to improve the tone reproducibility have been proposed in relation to the case that the image processing in optical recording/reproduction is effected by analog image signals and the case that the image processing in optical recording/reproduction is effected by digital image data. One known approach is that, as disclosed in the Japanese Patent Provisional Publication No. 63-212273, when a unit area (for example, whose side has a length which is 0.67 to 1.33 times the diameter of light spot for the exposure) due to division of a mesh spot (halftone cell) in a matrix form is used as the spatial and quantized unit, the unit area is vertically and horizontally divided into a plurality of small areas whereby the exposure for information recording is performed in units of a distance shorter than the diameter of the exposure light spot so as to improve the recording density and the tone reproducibility. There is a problem which arises with such a prior art technique where the tone is made by recording dots obtained by the exposure in units of the distance shorter than the light spot diameter, however, in that the exposure light source is required to be stably and nonlinearly intensity-modulated for allowing linear reproduction of the tone in the mesh spot.